Automatic or manual transmission? Your profile doesn't say.

If it is a manual, good idea to change it at that mileage.

If it is an automatic, it is better to have clean fluid in it but the process of changing it can lead to transmission failures. There is a long debate about the benefits of ever changing the fluid on higher mileage vehicles. Do a search on here and read some of the threads. The automatic transmission shops will tell you to change it, but will also know that it is those changes that create most of their rebuilt opportunities. The dealers will tend to tell you not to change it, as they don't want the liability associated with any failures post-change.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue